As means for inputting data in an information processing device such as an electronic computer, etc., there is known a bar code input system. The bar code input system has been widely used for sales management using separate data, data input for function check or operation/management of various devices for industrial or home use, etc.
The standard of such a bar code is explained in detail e.g. in Japanese Industrial Standard JIS 89550-1978; "Transistor" Technical Separate Volume, published by CQ Publishing Co., Jul. 1, 1984; Sensor Interfacing, No. 4, pp. 179-199 "Fabrication of Bar Codes"; etc.
FIGS. 3a and 3b show a scheme for decoding a bar code and the read-out waveform thereof. FIG. 3a shows symbols of a displayed bar code and FIG. 3b indicates a read-out waveform obtained by scanning the bar code indicated in FIG. 3a in the direction indicated by the arrow with a photo-electric converter. S in FIG. 3a shows a start code which is used for setting the initial state of the code reading device or as a reference for judging bar/space. C indicates a message code which indicates information (message) represented by this bar code. FIG. 3a shows that the code can also be read in the direction opposite to that indicated by the arrow.
The code reading device counts the number of clock signals corresponding to the interval between adjacent edges in the waveform in FIG. 3b which has two levels "H" and "L", obtained by transforming the bar code into electric signals using e.g. a self scanning type photo-electric converter. The information C is decoded from the count value thus obtained, and output to an information processing device in the form of binary data.
Further, since the bar code input system not only shortens considerably the time for data input by means of a keyboard, etc., it simplifies the input operation, and reduces the number of input mistakes. Because the photo-electric converter serving as an input device has no mechanically moving parts, the field of application becomes greater day by day.
This bar code input system is widely used e.g. for sales management whose principal data are the kind, the price, the number of sales, the sales territory, etc. for particular merchandises; presetting programs for VTR; control of microwave oven, room cooler, etc.; various information management by using various sorts of data; and operation and function check of various devices for industrial and home use.
As discussed above, the code reading device reading out a code such as shown in FIG. 3a counts the number of clock signals corresponding to the interval between adjacent edges in the waveform indicated in FIG. 3b. In the code reading device using the scanning type photo-electric converter, a bar code is scanned and decoded several tens to several hundreds of times to obtain a high reading out probability.